Screen plate for paper making machines



July 6, 1937. R. E. CLEVELAND SCREEN PLATE FOR PAPER MAKlNG MACHINES 2Sheets-Sheet 2 Filed Aug. 22, 1935 I, INVENTOR. Ralph f. Cleveland/l/bq/ ATTORNEY.

and materials, the most common size being aboutv Patented July 6, 1937.I

UNITED sTATEs SCREEN PLATE Foa PAPER MAKING MACHINES Ralph E. Cleveland,Waterbury, Conn.

Application August 22, 1935, Serial No. 37,293

6 Claims.

The invention `relates to screen plates of the type employed in papermaking machines for screening the wet pulp during the course of itsmanufacture int paper sheets.

These screen plates are formed of various sizes 42" long, 12" wide andthick, and the materials of which they are made generally being copper,brass or bronze.

In structure, the plates are formed with suc-- cessive Asets/ or groupsof parallel screen slots which, at the top or face side of the plates,are made very narrow in order to screen out all bres and particles thatexceed a certain desired size. These slots are usually provided by firstcutting a group of relatively Wide parallel grooves in the bottom sideof the plate to a depth such that they remaining unremoved metal is ofthe approximate thickness of 11g", and thereafter cutting the narrowface slots in communication with these grooves. Such formation of theslots, that is, the narrow portion at the face of thevplate opening intothe wide portion at the bottom, is intended to` facilitate clearance ofthe slots of the particles of paper pulp lwhich are carried therethroughin -the screening y operation. In service these screen plates corrode,and in conselquence the slots, particularly the upper narrow portionsthereof, -become widened and their edges become rough. When thishappens,uover sized particles and fibres pass through the screen. Alsoparticles of the paper pulp catch on the rough edges and tend to clogthe openings and thereby substantially reduce the screening efciency ofthe plate. Because of this, the plates must be mechanically cleanedeither vcontinuously or at frequent intervals, and the cleaning processtends to damage the plates and further enlarge the slot openings. Forsuch reasons it has been found' desirable to coat these screen plateswith chromium.-

Chromium plating provides ahard corrosion resistant coating. Through itsuse the wear and the roughening of the slot edges is much reduced withthe resultant maintenance of high screening capacity and desired slotdimension. Moreover, chromium plated screens require much less cleaning,and the abrasive effects of the cleaning are more successfully resistedby thechromium than by the underlying cuprous alloy. It has however beenfound that because of the known low throwing power of chromium, thechromium deposit on the inside faces of the slotsl at the upper narrowportions thereof, is extremely thin.l

In some uses of the plates, this extremely thin deposit has been foundsuiiicient to withstand corrosion; in many cases however, its resistanceis not suicient and the screen plate corrodes inside the slots with theconsequent undermining and collapse of the chromium plated edges.

Many expedients have been tried in an` attempt to overcome thisdiiiiculty by increasing the amount of chromium deposited within theslots. For example, attempts have been made. by regulating the locationof the anodes respective to the face and back lof the plate duringplating, to deposit a greater thickness of chromium on the back of theplate and inside the slot, without at the same time depositing too muchmetal upon the face of the plate. Another'expedient has been to reducethe thickness of the screen plateto M4", withthe intention of reducingthe amount of metal, which would intercept some of the current, betweenthe slots and the anode. Neither of these expedients nor others thathave been tried have been satisfactory, either because they do notattain the desired end or because they weaken the plate too muchinapproximatingit. l

With the foregoing in mind, it has been the object of the presentinvention to provide an improved chromium plated screen plate in whichthe objectionable features of those now in use will be eliminated, andwhich consequently will -be more durableand have greater screeningcapacity. Such object is attained by the improved screen platehereinafter described and claimed, and as illustrated in theyaccompanying drawings, in` which- Fig. 1 is a top plan view of a screenplate embodying my invention.

Fig. 2 is a bottom view of the same.

Fig. 3 is a cross section, `on an enlarged scale, through line 3-3 oi'Fig. 1.

Fig. 4 is a longitudinal section, on an enlarged scale, through'line I-Iof Fig. 1.

Fig. 5 is a cross section similar to Fig. 3, showing a modied formofconstruction.

Fig. 6 isabottom .-view, showing a modified form of construction.

Fig. '1 is a longitudinal section, on an enlarged scale, through line 11 of'Fig. 6.

' Fig. 8 is a cross section, similar to Fig. 3 showing a furthermodified form of construction.

Fig. 9 is across section, similar to Fig. 3, taken through aconventional form of screen plate, for the purpose of showing thedifference between it and my improved plate.

- having a series of successively arranged groups of juxtaposed parallelslots 2 opening from its top or face side downwardly through the bottomthereof. This plate, in use, is mounted in a socalled screen or screenbox, the bottom of which is constituted by a. exible diaphragm having avibratory movement which is effective to suck the watery pulp downwardlythrough the slots 2. 'I'his sucking action draws the .fibres that aresmaller than the slots, and that hence are of the desired dimensions,downwardly through said slots, the oversized particles and dirt beingvscreened out; and it is of the utmost importance that these bres shoulddrop or pass freely through the slots in order to maintain fullscreening efliciency. Free clearance of the slots will be substantiallymaintained provided the inner faces of the same are smooth, but in theevent of their becoming roughened through corrosion or otherwise, ashereinbefore seferred to, the bres will catch on the rough surfaces andhang therefrom, forming strings, which soon results in a clogging of theslots and a consequent impairment of the screening eiliciency of theplates. y

I`have discovered, as the result of long experimentation, that bymodifying the design of the usual screen plate, I am enabled to depositchromium upon the inside faces of the screen slots to a markedly greaterextent than heretofore, and sufcient to withstand corrosion for apractically unlimited period of time.

In the usual type of screen plate, as shown in Fig. 9, a series ofsuccessively arranged groups of parallel grooves 3 are cut in theunderside `of the plate I; these grooves usually being from 2" to 5"long, dependingon lthe style or use of the plate, and of a depth aboutfive-sixths of the thickness of the plate. Communicating with thesegrooves are the narrower screen slots 2' opening through the top or faceside of the screen plate. In chromium plating screen plates of thisconstruction, it has been found practically impossible, as hereinbeforeindicated, to obtain a thick deposit of chromium on the inside faces ofthe screen slots. This has been due in large part to the deep and narrowgrooves at the bottom of the plate, which constitute the lower part ofthe screen slots. In order to 'effect a deposit of chromium on the wallsof these, and particularly on the walls of the narrower communicatingface slots 2', it has been necessary to force the plating by the use ofhigh electrical current. This plating current, in-accordance with theknown laws of electro-plating, has a tendency to deposit the metalprimarily at the exposed faces and edges most accessible to its path,and also to deposit the metal in the areas within the slots at a veryrestricted rate. In addition, it has resulted in the production of gaseswhich substantially filled up the deep narrow grooves between the ribsand prevented such circulation of the plating solution through the slotsas was necessary to effect a good chromium deposit.

In accordance with my invention, as illustrated in Figs. 1 to 4, Iremove half thedepth or more of at least every alternate rib between thegrooves 3 at the underside of the screen plate, whereby comparativelywide open grooves are. left between the remaining ribs 4, into each ofwhich open two of the narrow screen slots 2. The partially removed ribsform reinforcing ridges-5 interposed between Ithe remaining ribs. Withthis construction of screen plate I have found that it becomesunnecessary to force the plating as heretofore, with the attendantobjections, as the wide grooves formed bythe elimination of certain ofthe ribs, each with a plurality of communicatlng screen slots, providesa sufciently free circulation of the plating solution through the slotsand a sufficiently -open path into and through them for the platingcurrent, as to effect a g ood chromium deposit on` the inside wallsthereof.

With the old construction of screen plate, the plating operationrequired at least 21/2 hours with the use of high current, in order toobtain even a thin, and usually incomplete, chromium deposit on theinside faces of the screen slots. With the improved plate of myinvention, I am enabled to obtain the same deposit within the slots in avery few minutes, and a strong healthy deposit in about one hour andforty-five minutes. Also, in the plating of the old style of screenplate, the use of a high current in forcing the plating of the insidefaces of the screen slots, resulted in a very brittle plating on theface of the screen plate, which was liable to crack andbreak olf underthe constant vibration to which the screen plate is subjected in use.When such cracking and breaking off occurs, corrosion sets in andundermines the adjacent chromium plate with resultant further breakingoff of the same. All of these objectionable features incident to forcedplating with the use of excessively high electrical current, areobviated by means of my improved construction, which assures asubstantially uniform deposit of .chromium on the entire surface of thescreen plate. that is, on the inside faces of the slots as well as onthe outer face 'of the plate, with the use of substantially less currentand in substantially less time than heretofore.

While I have described my invention as comprising a screen plate inwhich alternate ribs are partly removed for the purpose of obtainingrelatively wide grooves at the underside of the plate with at least twoscreen slot openings therein, it will be understood that the inventionmay be embodied in other forms of construction without departure fromthe spirit thereof. The above described embodiment is shown in Figs. 2,3, 4, 6 and '7` wherein the 'reinforcing ridges 5 are left to serve asstiffening or strengthening means for the plate. In some s tyles ofplates which are not Fig. 8. 'I'he structures shown in Figs. 5 and 8-are advantageously employed with staggered grooves, as shown in Figs. 2and 4, since this staggering assists in strengthening the plate. Whenthis construction is employed, the slots and the grooves in adjacentsets are positioned in a general end-to-end relation while theindividual grooves in one set are out of alignment with and staggeredwith respect to the opposed grooves in, adjacent sets. It will beobserved that each of these several constructions embody the essentialfeature of the invention, that is, the comparatively wlde grooves at theunderside of the plate having two or more of the narrow screen slotsopening Ainto each of the same, whereby the free entry and circulationof the .plating solution and of the current into and through the slotsis obtained.

Due to the improved plating upon the inside vention and the consequentlonger life of the,

screen plates thus obtained, I have found it pos-v sible to furtherdiminish the thickness of the uncut portion of the screen plate at thetop of the grooves 3. As hereinbefore described, this in theconventional plate is of the order of Through the use of my invention Ihave been enabled to reduce this thickness to a considerably smallerfigure, as will be apparent by a comparison of Fig. 8 with Fig. 9. 'Thisdiminished depth of slot results in an increased screening capacitywithout loss of accuracy in screen kslot size.

In the usual type oi' screen plate, the successive groups-of juxtaposedgrooves at the underside of the plate are separated by intervening endwalls extending the full depth of the plate, as

indicated at I0, Figs. 2 and 4. I have found however, that betterplating of the inside faces of the slots is obtained by reason of a moreready entry and circulation'of the plating solution and current throughthe slots, if the grooves are made continuous by a meeting of theiradjacent ends at a point Within the plate above its lower surface, asshown in Figs. 6 and 7. However, when 'the plates are to be used forheavy loads,v increased strength and stiffness may be obtained bykeeping the intervening end walls between the successive groups the fulldepth of y'the plate, as in Fig. 4, and forming the ribs Sof each groupin staggered lrelation to those of the adjacent groups, as shown inFigs. 2 and 4.

It will be understood from the foregoing that by reason of my improvedconstruction of screen p1ate,I can obtain a thick, uniform, andresistant chromium deposit on the entire surface of the plate, includingthe inside faces of the screen slots, and do this with less current andin a shorter period of time than heretofore done with the old type ofplate. I thus .obtaina cheaper, more durable, and consequently moreuseful chromium V'platedscreen plate than heretofore produced.

What I claim ls: 1. A screen plate for paper manufacture comprising aplate having successively arranged sets of parallel grooves withintervening ribs at its underside, and successively arranged sets ofparthe said sets of grooves meeting at theirY adja-v cent ends at apoint above the lower surface of the plate, said plate being coated withchromium. 2. A screen plate for paper manufacture, comprising a platehaving successively arranged sets of juxtaposed parallel grooves withintervening Vribs at its underside, and correspondingly arranged sets ofjuxtaposed parallelslots in its upper or face side, the slots runningparallel with said grooves and at least two ot said slots opening intoeach of the said grooves the slots and grooves in vadjacent sets beingpositioned in a general end-to-end relation and, the individual groovesin:` one set being out of alignment with and staggered with respect tothe opposed grooves in the adjacent sets, said plate being coated withchromium.

3. 'I'he screen plate of claim4 wherein the depending distance of'saidreinforcing ridges is less than half that of said ribs.

4. A chromium plated screen plate for paper manufacture comprising aplate having an upper or face side and a lower or discharge side,successivelyv arranged sets of juxtaposed parallel slots in its upperside and successively arranged sets of juxtaposed parallel grooves inits lower side, at least two of which slots open into each of saidgrooves, low reinforcing ridges between the slot openings, in eachgroove, depending to a substantially lesser extent than the ribs formingthe walls of the grooves, said grooves meeting at their adjacent ends ata point above the lower surface of the plate.

5. The screen plate of claim 4 wherein the individual grooves of eachsetl run parallel to said posed, parallel grooves in adjacent sets.

6. A chromium plated screen plate for paper manufacture comprising aplate having an upper or face side and a lower orl discharge side,successively arranged sets of juxtaposed parallel slots in its upperside, the slots in each set being aligned with the slots of adjacentsets, correspondingly arranged sets of juxtaposed parallel grooves inits lower side. said grooves being parallel to and communicating withsaid slots, the individual grooves in ,each set being out of alignjmentwith and being staggered with respect to allel slots in its upper orface side, at least two of which slots open into each of the saidgrooves.

the opposed grooves of the adjacent sets. f

